Self-aligning screw driver



July 23, 1968 95; FOREST 3,393,721

SELF-ALIGNING SCREW DRIVER Filed May 9, 1966 INVENTOR M k 'X M mudm ATTORNEYS.

Unit d W8 m 0 3,393,721. SELF-ALIGNING SCREW DRIVER Taber de Forest, Town St., East Haddam, Conn. 06423 Filed May 9, 1966, Ser. No. 548,634 10 Claims. (Cl. 145-50) ABSTRACT OF THE DISCLOSURE A screwdriver with a blade than can rock with respect to the axis of the shank of the tool. The rocking movement is in the plane of the blade so that the shank can rotate the blade with a universal joint action when'the axis of the shank is out of alignment with the axis of a screw on which the screwdriver is being used. An elastomer, or other resilient means, carried by the shank, urges the blade into alignment with the shank but yields to permit the universal joint action. The resilient means contact with the screwdriver blade adjacent to. corners at the opposite ends of a top face of theblade-which is located in a channel formed in the lower end of the shank.

Brief'description 0] the invention This invention relates to screwdrivers and more especially to screwdrivers that are intended to be rotated by power. t

- Power screwdrivers. have important advantages on jobs where a large number of screws are to be driven. They put the screws in much faster than can be done; with manually rotated-screwdrivers, and theyalso obtain more uniform fastening inthat the power can be made to apply equal torque to all screws.

It is an object of this invention to provide an improved screwdriver for power operation, and more particularly to provide a power screwdriver that requires less skill to operate it. One of the principal problems with power screwdrivers is the tendency of the screwdriver blade to jump out of the screw slot when the blade is tilted slightly out of line with the screw. If one side of the edge of the screwdriver is raised above the edge of the screw slot, then the torque of the screwdriver, in effect, raises the entire screwdriver blade out of the slot by a cam action against one edge of the slot.

It is an object of this invention to provide a screwdriver with a blade and a shank connected to one another for limited angular movement about a pivot connection so that the shank can tilt out of line with the screw while the blade remains in full engagement with the slot in the screw.

In the preferred construction of the invention, there are resilient means for holding the blade and shank in substantial alignment with one another, but this resilient means yields to permit misalignment which is caused when a chuck that holds the shank is tilted with respect to the longitudinal axis of the screw. This centering bias is important because it hold the blade in a center position when not in a screw slot and thus facilitates the original engagement of the blade with each screw which is to be driven.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

3,393,721 Patented July 23, I968 lcc Brief description of the drawing In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGURE 1 is a side elevation of a screwdriver made in accordance with this invention, the screwdriver being shown in engagement with a screw;

FIGURE 2 is an end view of the screwdriver and screw shown in FIGURE 1;

FIGURE'7 is a side elevation of a fifth modified form of the invention.

Description 0 the preferred embodiments FIGURES l and 2. show a screwdriver having a shank llland a blade 12. The shank is shown as hexagonal in cross section, but other shapes can be used; There is a channel 14 in a bottom end face 16 of the shank. The blade 12 is slightly narrower than the channel 14 so as to be freely movable in the channel; and the blade 12 is connected to the shank 10 by a pivot 18.

The blade 12 has a bottom edge 20 for engaging a slot 22 in a screw 24, and the blade 12 is held in alignment with the shank 10, as shown in full lines in FIG- URE l, by yielding means comprising an elastomer 28 located between the top of the blade 12 and a concave face 30 of the channel.

The face 30 of the channel which is opposite the open end of the channel, will be referred to herein as the bottom of the channel since that is the usual nomenclature for channels; and the reason for the bottom face 30 being located above the top of the top of the blade 12 is because the channel 14 is inverted.

The shank 10 can move into an angular position with respect to the blade 12 as indicated in dot-an-d-dash lines in FIGURE 1. The extent of this angular movement, or misalignment, depends upon the clearance between the top of the blade 12 and the ends of the channel bottom 30; and also upon the compressibility of the elastomer 28 which is placed in the clearance between the blade 12 and the channel bottom 30.

The blade 12 is preferably not a tight fit in the slot 22 and this permits the screwdriver to rock right and left in FIGURE 2, i.e., in a plane at right angles to the direction in which the blade moves when it rocks about the axis of its pivot 18. Because of these two possible angular movements, in planes normal to one another, the blade is capable of transmitting torque from the shank 10 to the screw 24 with what is, in effect, a universal joint action.

In order to have stability in operation of the screwdriver, the direction of the thrust of the shank 10, when the shank is at its maximum angle of misalignment with respect to the blade 12, this direction of thrust being indicated by the line 34 in FIGURE 1, should intersect the screw within the limits of the ends of the screw slot. If the line 34 is beyond the end of the screw slot, then the operation of the pivot connection becomes unstable, it may be said, therefore, that stable operation is obtained when the construction is such that a normal from the axis of the pivot 18 to the end 20 of the blade makes an angle 38 with a line from the axis of the pivot to the end of the blade which is greater than the maximum angle of misalignment to which the blade and shank can move with respect to one another.

FIGURE 3 shows a modified construction in which corresponding parts are indicated by the same reference characters as in FIGURES 1 and 2 but with a prime appended. In place of the channel having the concave bottom, as in FIGURES l and 2, FIGURE 3 shows a channel having a convex bottom 30 with an elastomer 28' filling the clearance between the top of the blade and the bottom face 30' of the channel. This construction has the advantage that there is a thicker section of elastomer at the places where the elastomer must be compressed the furthest in order to obtain angular movement of the blade 12' with respect to the shank 10.

FIGURE 4 shows another modified construction in which parts are indicated by the same reference characters as in the other views but with a letter a appended. This construction differs from that of FIGURE 3 only in that a spring 40 is substituted for the elastomer. This spring 40 can be connected to the shank 10a by adhesive or by other fastening means and the spring 40 has rounded end portions which bear against the top of the blade 12a near opposite ends of the blade to give the blade a bias toward an aligned position; but the spring 40 constitutes a yielding means, as in the case of the elastomers of FIGURES 13, so that the shank and blade can move into misalignment.

FIGURE 5 shows another modified construction with the corresponding parts shown by the same reference characters as in the other views but with a letter b appended. In this construction shown in FIGURE 5, the yielding means for holding the blade and shank in alignment contsitutes a sleeve 42 which fits closely around the shank 10b and which has resilient end portions 44 extending downwardly in position to contact with the top edges of the blade 12b when the sleeve 42 is in its lowered position, as shown in dot-and-dash lines in FIGURE 5.

FIGURE 6 shows another modified construction with the letter appended to the reference characters and with t a short length of tube or collar 46 fitting closely around the shank 10c and hugging the shank, as in the case of the sleeve 42 of FIGURE 5. This collar 46 is made of elastomer and can be pushed down on the shank 100 until it contacts with the upper end of the blade 12c. When in this position, the collar 46 is held against upward movement by friction with the shank and the blade 100 can not rock on the pivot 180 without distorting the collar 46. If greater freedom of pivotal movement is desired, after the blade 100 has been engaged with the slot of a screw, the collar 46 can be pulled back manually out of engagement with the blade, and the same can be done with the spring means of FIGURE 5.

When the sleeve 42 of FIGURE or the collar 46 of FIGURE 6 is pulled back, the angular movement of the blade is limited by the bottom 30b or 30c of the channel, even though there is no elastomer in the channel.

FIGURE 7 shows another modified construction with the letter d appended to the reference characters. In this construction there is a recess 50 in the bottom 30d of the channel and a leaf spring 52 is securely held at its upper end in the recess 50. The lower end of the leaf spring 52 engages in a cross slot 54 in the top of the blade 12:] and when the leaf spring is undistorted, the blade 12d is held in alignment with the shank d.

The recess 50 has diverging side walls which permit flexing of the spring 52 so that the blade 12d can rock about the pivot 18d into various angles of misalignment, as in the case of the other modifications of the invention.

The preferred embodiments of the invention have been illustrated and described, but changes and modifications can be made and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. A screwdriver including a shank, a channel extending across one end of the shank, a blade having a working end for engaging a depression in a screwhead, said blade extending into the channel and having a top face spaced from a confronting face at the bottom of the channel and with corners at the opposite ends of the top face adjacent to opposite ends of the channel, a pivot connection between the blade and the shank, and resilient .means carried by the shank in position to contact with the blade adjacent to both of said corners for yieldably holding the blade in substantial alignment with the shank.

2. The screwdriver described in claim 1 characterized by the working end of the blade being elongated in one direction corresponding to the length of the slot of the screw with which the blade is to be used, and the pivot extending in a direction transverse of a plane that contains the longitudinal axis of the shank and the elongated end of the blade.

3. The screwdriver described in claim 2 characterized by abutment means limiting the angular movement of the blade with respect to the shank, the pivot being located above the center region of the blade and the angle between 21 line from the pivot normal to the working end of the blade and a line from the pivot to an end of said working end of the blade being greater than the maximum angle of misalignment of the blade with respect to the shank.

4. The screwdriver described in claim 1 characterized by the blade having an edge that engages a screw slot and about which the blade can rock on the screwhead in one direction, and the pivot extending in a direction with an axis about which the blade can rock 'with respect to the shank at right angles to the direction of the rocking of the blade on the screwhead whereby the blade provides a universal joint action through which torque from the shank is transmitted to the blade.

5. The screwdriver described in claim 1 characterized by the resilient means for holding the blade in substantial alignment with the shank including spring means carried by the shank and extending downward into contact with the sides of the blade adjacent to said corners.

6. The screwdriver described in claim 5 characterized by the corners of the blade being above the pivot and projecting beyond the sides of the shank when the blade is in substantial alignment with the shank.

7. The screwdriver described in claim 6 characterized by the blade tapering upward toward its maximum width at its upper end and the resilient means including a sleeve that hugs the shank and part of which extends downward into contact with the top portion of the blade.

8. The screwdriver described in claim 7 characterized by the sleeve being made of an elastomer.

9. The screwdriver described in claim 1 characterized by the confronting faces of the blade and the bottom of the channel being spaced from one anotherby different distances at different locations along the length of the channel, the pivot extending across the channel and the resilient means being between said confronting faces of the blade and the bottom of the channel, and being of different height at locations where the spacing of the confronting faces is different whereby the resilient means is held against endwise movement in the channel by said different spacing of the confronting faces, said yieldable means being compressed on one side or the other by References Cited swinging of the blade about its pivot in either direction. UNITED STATES PATENTS 10. The screwdriver described in claim 1 characterized by the resilient means being located between the cOngz g fornting faces of the blade and the bottom of the chan- 5 nel, and said resilient means being an elastomeric insert FOREIGN E T and the bottom of the channel and the elastomeric insert 26,634 4/1909 S d having confronting concave and convex faces curved along the length of the channel to hold the elastomeric ROBERT RIORDON Pnmmy Exammflinsert against endwise displacement in the channel. 10 R. V, PARKER, Assistant Examiner. 

